Cold weather is common around the year in the Arctic, Antarctica, as well as at high elevations, and during winter in temperate areas. Cold weather is part of everyday life for the residents of these areas, as well as travellers who pursue activities such as Nordic skiing, alpine skiing or mountaineering.

Cold weather is potentially lethal. In the Northern Hemisphere, several homeless people die from hypothermia every winter. Cold threatens health by two distinct mechanisms, which occur separately: frostbite and hypothermia. Frostbite is a result of freezing of exposed skin and has similar effects as a burn, usually affecting the face, ears, fingers and toes. Hypothermia is lowering the core body temperature due to inadequate whole-body protection from cold, and may occur even in relatively mild weather if it rains and the clothes get wet.

Keep in mind that clothing that feels adequate for short walks may be all too cold when you have to stay outdoors for extended periods. Also remember that nights and early mornings may be much colder than the day. With windy or rainy conditions, more protective clothing is required. Trying to just "tough it out", which may be possible in warmer climates, can be dangerous.

Near and below freezing point, you should cover your entire body. Don't neglect gloves, headwear or scarves. A naked head may not feel cold, but it can quickly drain the body of heat, and risks frostbite of the ears, which can be very painful. At colder temperatures you should be careful where clothes join, such as at wrists, back and neck; too short a shirt will cool the back and an exposed wristwatch may cause frostbite in extreme temperatures. A hood protects the ears and (if extending forward) the face. Scarves or balaclavas make the experience much more comfortable by keeping the neck warm, instead of having to keep the shoulders in a permanent shrug.

Pay great attention to the footwear. Boots should be high enough for snow not to enter (preferably also protected in other ways). The sole must be thick enough and the boot itself and socks (double pairs) should be warm. Use warm removable insoles. Near the freezing point boots must be protected from wet snow, e.g. by waxing. Below -5°C moisture is less of a problem, but sunshine may still melt snow on the boots.

When it comes to materials, cotton is inefficient for heat preservation. Natural fur, duck or goose down, wool and microfiber are suitable. Underwear is the most important to select, since if one breaks a sweat, cold and damp cotton feels like being dipped in a pool of cold water. Although jeans can protect from even freezing temperatures, below ca. -15 °C wearing long underwear (long johns) is advisable, more so if skiing or otherwise exposed to wind.

Several layers of clothing are better than a single warm coat. Usually one should have at least a wind stopping outer layer, a warm sweater for breaks and other clothing as needed. The clothing should allow easy adjustments when you enter a windy area or start climbing a steeper hill. You should be able to add or remove layers depending on overall temperature. Clothing sufficient at -5 °C is not sufficient at -20 °C.

When staying overnight in a tent, hut or other primitive lodgings clothes should be easy to dry. Boots or gloves with thick lining can be problematic.

Special attention should be paid to clothing babies, children and youth correctly. Children need warmer clothes than adults due to a higher skin area-to-weight ratio; a baby needs one layer more clothing than an adult. Worse, children are unable to clearly communicate discomfort or the symptoms of frostbite or hypothermia.

Keeping warm requires energy and is much harder when hungry - or tired. Have enough food and enough snack and food breaks.

Raisins and fructose pills are good for instant energy. Chocolate, while high in energy, loses its taste when cold.

More drinking water is needed than in mild weather. Warm drinks, such as tea, coffee or hot chocolate, are good also for the mood. Water or drinks in ordinary bottles will freeze, use thermos bottles and local supplies (e.g. snow) instead, or keep a small bottle in the pocket inside the jacket. Avoid alcohol, as it affects blood circulation in the skin.

Rest is important, as keeping warm is more difficult - and making bad decisions more easy - when tired. But when really tired you must not rest until having found safe shelter, as continuing after the rest may be difficult, especially if part of the company suffers from hypothermia. In such cases, do not let anybody sit down or stay still until the shelter is ready, warm and comfortable. Make sure everybody puts on their rest sweaters also on ordinary breaks.

Cold weather is much less dangerous when not combined with wetness or wind. Adjust labour and clothing to avoid sweating. Avoid having your clothes and shoes get wet by melting snow (or by water). Avoid open windy terrain if you are near your limits. Get shelter for the breaks. Do use your dry spare clothes as needed. Changing clothes may be uncomfortable, but not changing will prove more so.

If lost, you can dig a pit in the snow for protection against the wind. A more elaborate option is building a wall from igloo bricks, which can protect a tent.

Cotton fares very badly in cold weather when moist or wet. One should avoid cotton undershirts if exercising and sweating; instead, wool and artificial fibers retain more of their insulating ability when moist. The same applies to socks; woolen socks are better than cotton socks.

Getting drenched at freezing temperatures, as in falling into water, is an emergency. Without a change of clothes or going inside into a warm room, hypothermia quickly sets in. In cold water, useful movement is possible up to 10 min and survival up to 30 minutes. However, the immediate cold shock response is more likely to cause a heart attack or drowning.

Cars should be equipped with a cabin air heating system for a comfortable ride and for safety. Moreover, the humidity from occupants breathing tends to frost over the windows, and removing the frost requires flowing warm air. Gas stations sell winter-grade diesel and gasoline in winter; summer-grade diesel may cloud and freeze over. Car engines can be pre-heated with engine block heaters to prevent starting problems. Winter driving is more difficult than summer driving because of slippery roads; the traction is often too weak to permit tight turns at a higher speed more than about 30 km/h.

When biking, snowmobiling or motorbiking, much more protective clothing is required than when walking. The relative wind easily finds its way through gaps and holes in the clothing. Protective glasses, face-covering balaclavas and possibly hard face shields are used. Motorcycle helmets are usually equipped with vents that can be shut for cold weather. However, bike helmets are built for letting the wind in rather than keeping it out, and the cold wind can cause tremendous headaches. Using a tight-fitting warm hat is necessary, and some cyclists tape over the openings in the helmet from the inside.

Staying outdoors overnight in freezing weather should be done only with great caution and careful planning, in a shelter, with a good enough sleeping bag and with good insulation to the ground (air mattresses for the beach are worthless, mattresses for hiking not necessarily enough). Everything outside the sleeping bag will freeze.

Most good sleeping bags are nowadays marked with a "comfort" and an "extreme" temperature. If night temperatures are expected to come near the "extreme" point, you will not want to sleep outdoors without fire and good shelter. Remember that most weather forecasts cite day temperatures.

If you intend to stay the night by a fire, be sure to collect enough firewood before going to sleep and to have a watch all the time. Skill is needed to use the fire effectively.

When staying overnight indoors, make sure to get shoes and clothes properly dried (without overheating them). Unlike at home, things will not dry automatically in a wilderness hut.

If you are away from inhabited areas you must be able to cope with emergencies yourself, at least for some time. Somebody who becomes disabled or wet (stepping through the ice of a river or even a ditch) may soon risk hypothermia.

A disabled person must have good insulation from the ground and much warmer clothing than those able to stay warm by moving. You probably have hiking mattresses and blankets that can be used. Sharing a sleeping bag (there are also models that can be combined) is a very good way of keeping somebody warm. You might want to build some kind of shelter (e.g. a big cloth rigged with ropes) and make a fire. In some cases you will have to construct some kind of sledge (e.g. two young trees with a platform between them, carried by the thicker forward end), but usually it is better to have the help come to you.

If somebody gets thoroughly wet boots or clothes, they must by changed without much delay. There might be a house nearby, where you can seek shelter. Otherwise you hopefully have enough spare clothes. Wet boots can still be used by having the foot and warm dry socks in a plastic bag inside the boot. You might want to camp soon to be able to dry the clothes at a fire (which will take a lot of time).

An acute threat of hypothermia is an emergency. Therefore, if exposed and without means of recovery from the situation, one should promptly ask for help, or in the absence of other means, seek shelter by any means necessary, not wait for the situation to get worse. In the event of getting lost in a foreign city at night without warm clothers or a cellphone, one should contact emergency services or anyone nearby, not wander around until the hypothermia clouds the consciousness. It is especially important to tell youth and children to not wander around if they get lost, but contact an adult immediately.

Frostbite means damage caused to skin and other tissues due to freezing. Cooling the skin is painful, so you should react to it as soon as the pain appears, since sensation is lost on further cooling and then damage occurs unnoticed. The condition is much like burns. The nose, ears, chin and cheek are the body parts most easily affected, especially in windy weather, and like sunburn the condition might not get noticed until too late. Watch out for white spots in your fellows' skin. Fingers and toes may also get frostbitten, but you will more easily notice them getting uncomfortable. Also, touching metal surfaces with bare skin can cause frostbite. First aid is gently warming the affected area with a warm body part, such as the armpit, and protecting it from further coldness.

Hypothermia is overall reduced body temperature. It will lead to loss of initiative, sluggish thinking and irrational behaviour. Keeping on walking even when tired is important, not only to reach shelter, but also to keep warm. In severe cases it is important to warm the victim slowly, without massaging, because cold blood from arms and legs may cause vital organs to fail.

The elderly, the disabled and children are more vulnerable to frostbite and hypothermia. Children might try to lick a metal rails or other surfaces, which instantly freezes the tongue fast, and the usual response, jerking back, tears off the frozen part of the mucous membrane, resulting a bleeding wound. Many children in cold countries have tried this once, but not twice.

Have fun! Skiing, snowmobiling or snowshoeing in an Arctic night, with northern lights shining, is an unforgettable experience. Furthermore, whole modern societies live and work in cold climates, including children, the elderly, and the disabled. Winter or snowfall is barely an obstruction, with life in the society continuing normally. Taking some simple precautions and using common sense is all that is necessary for a traveller.